Magnetic fields and the dynamics of the outer disk of spiral galaxies

2005 ◽  
Author(s):  
Eduardo Battaner
Keyword(s):  
Magnetic Fields ◽  
Spiral Galaxies ◽  
Outer Disk

scholarly journals Magnetic Fields in the Disk-Halo Interface

1991 ◽  
Vol 144 ◽  
pp. 169-174
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Interstellar Gas ◽  
Outer Disk ◽  
Vertical Field ◽  
Interstellar Gas In Galaxies ◽  
Halo Gas

A review is given of large-scale magnetic fields in disks and halos of spiral galaxies. A particular attention is given to vertical field structures, and we discuss their origin and implication on their interaction with halo gas. We point out that the disk-halo magnetic interface plays an important role in circulation of interstellar gas in galaxies, in particular a large-scale circulartion from the galactic center to outer disk regions.

Density waves in the outer disk of spiral galaxies

2010 ◽  
Author(s):  
G. Bertin ◽  
N. C. Amorisco ◽  
Giuseppe Bertin ◽  
Franca De Luca ◽  
Giuseppe Lodato ◽  
...  
Keyword(s):  
Spiral Galaxies ◽  
Density Waves ◽  
Outer Disk

The Distribution of Radio Polarisation in Three Southern Galaxies

1991 ◽  
Vol 9 (2) ◽  
pp. 266-268
Author(s):  
J. I. Harnett ◽  
U. Klein ◽  
R. Wielebinski ◽  
R. F. Haynes
Keyword(s):  
Cosmic Rays ◽  
Magnetic Fields ◽  
Radio Telescope ◽  
Spiral Galaxies ◽  
Total Power ◽  
Transport Mechanisms ◽  
Contour Plots ◽  
Preliminary Study ◽  
Poloidal Magnetic Fields

AbstractWe are studying the distribution and morphology of magnetic fields in southern face-on and edge-on galaxies with the intention of clarifying the distribution, lifetimes and transport mechanisms of cosmic rays, and investigating the intensity and orientation of the disc, halo and poloidal magnetic fields. As a preliminary study, before the Australia Telescope was available, we observed a sample of well-known southern spiral galaxies with the Parkes radio telescope.Here, we present the resulting polarisation images for three galaxies, NGC 253, M 83 and NGC 4945, which were observed at 4.75 GHz and 8.55 GHz. The corresponding total power contour plots have been already published by Harnett et al. (1989a, 1990).

scholarly journals Magnetic Fields in Disks and Halos of Spiral Galaxies

1991 ◽  
Vol 144 ◽  
pp. 267-280 ◽  
Author(s):  
Rainer Beck
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Coronal Holes ◽  
Azimuthal Angle ◽  
Total Strength ◽  
Radio Halo ◽  
Star Formation Activity ◽  
Energy Equipartition ◽  
Field Lines

Spiral galaxies host interstellar magnetic fields of 4-15 μG total strength. A significant fraction of the field lines shows large-scale structures. At face-on or moderately inclined view, the field lines run generally parallel to the spiral arms, either with uniform direction with respect to azimuthal angle (axisymmetric spiral, ASS), with one reversal along azimuthal angle (bisymmetric spiral, BSS), or with spiral orientation without dominating direction.At edge-on view, the field is concentrated in a thin disk, often surrounded by a thick radio disk with field lines mostly parallel to the plane, similar to the quadrupole-type dynamo field. Radio polarization data from NGC891 indicate that the thermal gas seen in Hα is responsible for Faraday depolarization. The required scaleheight of the field of ~4 kpc is comparable to the value expected in case of energy equipartition between magnetic fields and cosmic rays. The interacting edge-on galaxy NGC 4631 shows a much larger radio halo with field lines perpendicular to the disk, possibly driven by a strong galactic wind or the result of a dipole-type halo field.Field lines bending out of the plane are also visible in face-on galaxies as regions with high rotation measures and low star-formation activity. The resemblance to the phenomenon of the solar corona suggests to call them “galactic coronal holes”.

scholarly journals Galactic Winds and Magnetic Fields from Spiral Galaxies

1990 ◽  
Vol 140 ◽  
pp. 177-181 ◽  
Author(s):  
H.J. Völk ◽  
D. Breitschwerdt ◽  
J.F. McKenzie
Keyword(s):  
Cosmic Rays ◽  
Magnetic Fields ◽  
Mass Loss ◽  
Magnetic Structure ◽  
Essential Role ◽  
Spiral Galaxies ◽  
High Energy ◽  
Energy Component ◽  
Galactic Winds ◽  
High Energy Component

Concentrating on our own Galaxy we discuss the dynamics of the outer halo, its magnetic structure and the occurrence of a supersonic mass loss in the form of a Galactic wind. The cosmic rays, as the nonthermal high energy component, de facto not influenced by gravity, play an essential role in the wind dynamics.

scholarly journals Dynamo in Astrophysics

1990 ◽  
Vol 140 ◽  
pp. 83-89
Author(s):  
A.A. Ruzmaikin
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Turbulent Flow ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Clusters Of Galaxies ◽  
Magnetic Structures ◽  
Random Magnetic Field ◽  
Astrophysical Objects

The fast dynamo acting in a turbulent flow explains the origin of magnetic fields in astrophysical objects. Stellar cycles and large-scale magnetic fields in spiral galaxies reflect the behaviour of a mean magnetic field. Intermittent magnetic structures in clusters of galaxies are associated with random magnetic field.

Magnetic Fields and Star Formation for the ANS Sample of Galaxies

1990 ◽  
Vol 140 ◽  
pp. 233-234
Author(s):  
J. Stryczynski
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Field Data ◽  
Spiral Galaxies ◽  
Magnetic Field Data ◽  
Uv Range

From the literature we collected radio and magnetic field data for the ANS spiral galaxies. We suggest that the groups of objects, as revealed in the UV range, do not differ in magnetic field strength, although statistics of the sample are very poor.

scholarly journals The Z Velocity Dispersion of Outer H I Disks

1996 ◽  
Vol 169 ◽  
pp. 489-495
Author(s):  
John M. Dickey
Keyword(s):  
Velocity Distribution ◽  
Velocity Dispersion ◽  
Spiral Galaxies ◽  
Thermal State ◽  
Stellar Disk ◽  
Interstellar Gas ◽  
Heating And Cooling ◽  
Outer Disk ◽  
Atomic Gas

The velocity dispersion of the interstellar gas measured perpendicular to the disk in face-on spiral galaxies shows a remarkable consistency. Typically the width of the velocity distribution decreases monotonically with increasing galactic radius through the luminous, stellar disk; but in the outer disk where there is gas but no stars the velocity dispersion is συ ≃ 7 km s−1 with a scatter of 2 km s–1 at most from one position to another and from one galaxy to another. Trying to understand this number raises questions about the thermal state of the H I in outer, gaseous disks. The most important issue is to understand the dominant heating and cooling processes for the atomic gas.

scholarly journals Magnetic Field Strengths of Spiral Galaxies and the Far-Infrared/Radio Correlation

1990 ◽  
Vol 140 ◽  
pp. 241-241
Author(s):  
A. J. Fitt ◽  
P. Alexander
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Distribution ◽  
Detection Rate ◽  
Spiral Galaxies ◽  
Far Infrared ◽  
Magnetic Field Distribution ◽  
Selection Effects ◽  
The Magnetic Field ◽  
Field Strengths

We have calculated equipartition magnetic fields for a complete, optically-selected sample of 165 spiral galaxies. The magnetic field distribution (fig. 1) is type independent, and shows remarkably little spread in values, around 1 decade in B. This is not due to selection effects because of the nature of the sample and the 95 percent detection rate.

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